Virtual Maximum Ratio Transmission for Downlink OFDMA Relay-based Networks

In this paper, a novel and practical transmission scheme for a Multiple Input Multiple Output–Orthogonal Frequency Division Multiple Access (MIMO-OFDMA) relay-based network is proposed and evaluated. We coin the term Virtual Maximum Ratio Transmission (VMRT) for the scheme which obtains diversity and array gain at both links in a two-hop transmission, while keeping the complexity low. Besides, the requirements of Channel State Information needed at the different network elements such as the Base Station, Relay Station or User Terminals are also limited, and so the feedback. The obtained global performance by using proposed VMRT outperforms other schemes. Diversity gains larger than 6 can be easily obtained with a reduced number of relays. For this reason, VMRT is a good candidate to achieve high speed transmission or increase coverage and reliability in slow varying channels for relay-based networks.